1. Field of the Invention
The present invention relates to an apparatus and methods for facilitating the connection of tubulars. More particularly, the invention relates to an interlock system for use with two or more tubular holding apparatus during the assembly or disassembly of tubulars. More particularly still, the invention relates to an interlock system for use with a top drive and a spider during the assembly or disassembly of tubulars.
2. Background of the Related Art
It is known in the industry to use top drive systems to rotate a drill string to form a borehole. Top drive systems are equipped with a motor to provide torque for rotating the drilling string. The quill of the top drive is typically threadedly connected to an upper end of the drill pipe in order to transmit torque to the drill pipe. Top drives may also be used in a drilling with casing operation to rotate the casing.
To drill with casing, most existing top drives use a threaded crossover adapter to connect to the casing. This is because the quill of the top drives is typically not sized to connect with the threads of the casing. The crossover adapter is design to alleviate this problem. Generally, one end of the crossover adapter is designed to connect with the quill, while the other end is designed to connect with the casing. In this respect, the top drive may be adapted to retain a casing using a threaded connection.
However, the process of connecting and disconnecting a casing using a threaded connection is time consuming. For example, each time a new casing is added, the casing string must be disconnected from the crossover adapter. Thereafter, the crossover must be threaded to the new casing before the casing string may be run. Furthermore, the threading process also increases the likelihood of damage to the threads, thereby increasing the potential for downtime.
As an alternative to the threaded connection, top drives may be equipped with tubular gripping heads to facilitate the exchange of wellbore tubulars such as casing or drill pipe. Generally, tubular gripping heads have an adapter for connection to the quill of top drive and gripping members for gripping the wellbore tubular. Tubular gripping heads include an external gripping device such as a torque head or an internal gripping device such as a spear. An exemplary torque head is described in U.S. Patent Application Publication No. 2005/0257933, filed by Pietras on May 20, 2004, which is herein incorporated by reference in its entirety. An exemplary spear is described in U.S. Patent Application Publication Number US 2005/0269105, filed by Pietras on May 13, 2005, which is herein incorporated by reference in its entirety.
During tubular running or makeup/breakout operations, the top drive and the spider must work in tandem, that is, at least one of them must engage the casing string at any given time during casing assembly. Typically, an operator located on the platform controls the top drive and the spider with manually operated levers that control fluid power to the slips that cause the top drive and spider to retain a casing string. At any given time, an operator can inadvertently drop the casing string by moving the wrong lever. Conventional interlocking systems have been developed and used with elevator/spider systems to address this problem, but there remains a need for an interlock system usable with a top drive/spider system such as the one described herein.
There is a need therefore, for an interlock system for use with a top drive and spider to prevent inadvertent release of a tubular string. There is a further need for an interlock system to operate the top drive and the spider based on a load held by the top drive or the spider.